What is ALT?
Alanine aminotransferase (ALT) is an enzyme concentrated in liver cells. When the liver is inflamed or injured, ALT leaks into the bloodstream, so an elevated ALT is a sensitive, fairly liver-specific sign of liver damage. It is a core part of a liver panel and increasingly used to screen for fatty liver disease.
Why it matters
ALT elevations can be the first sign of fatty liver disease now the most common liver condition as well as hepatitis, medication effects, and alcohol-related injury.
What it measures
The blood concentration of ALT, interpreted alongside AST and other liver tests.
Reference & optimal ranges
Reference ranges vary by lab, assay, age, and sex. The ranges below reflect commonly published adult intervals and are for education only always interpret results with the range printed on your own lab report and a clinician.
High ALT indicates liver cell injury, most commonly from fatty liver disease, alcohol, medications, or viral hepatitis.
Common symptoms
- Often none
- Fatigue
- Right upper abdominal discomfort
- Jaundice (if advanced)
Potential causes
- Non-alcoholic fatty liver disease (NAFLD)
- Alcohol use
- Viral hepatitis
- Medications (including acetaminophen, statins)
- Obesity and insulin resistance
Low ALT is generally not clinically significant.
Common symptoms
- None
Potential causes
- Normal variation
- Sometimes vitamin B6 deficiency
How to improve your ALT
Lifestyle
Limit alcohol
Alcohol is a leading cause of elevated liver enzymes; reducing intake often lowers ALT.
Nutrition
Reduce sugar and lose excess weight
Weight loss and cutting added sugar are the most effective ways to improve fatty-liver-related ALT elevations.
Exercise
Regular exercise
Reduces liver fat independent of weight loss.
Sleep
General health
Supports metabolic health tied to liver function.
Frequently asked questions
Scientific references
- ALT Blood Test MedlinePlus, U.S. National Library of Medicine
- ALT Test Testing.com
Educational information, not medical advice. This page is for general education and does not replace diagnosis or treatment by a licensed clinician. Do not start, stop, or change any medication, supplement, or treatment based on this content. Reference and optimal ranges vary between laboratories interpret your results with the range on your own report and a qualified professional.